Answer: This is a clear common case of fraudulent misrepresentation by both broker and selller, since the real estate agent (broker) has legal obligation of being a trustworthy party telling the real condition of a given property before any transactions. Similarly responsible is the seller, who has to inform in a proper form any known or suspected structural problems before concluding the business.
Although broker and seller may declare innocent misrepresentation - telling that "we absolutely did not know about that" - the judgement will be led by attached evidence - like photos and videos of the plumbing - easy to be alleged as proof of, at least, negligent conduct of the demanded party.